The plant cytotoxin ricin is a heterodimer. The A chain, known to be a specific N-glycosidase, has a prominent active site cleft. The B chain is a two-domain lectin, which arose from the replication of a primitive sugar binding peptide. The B chain subunit of ricin (RTB)1 binds to mammalian cell membranes by recognizing galactose-containing receptors. RTB has two domains each with three subdomains; tripeptide kinks in the loops from subdomains 1alpha, 1beta, 2alpha, and 2gamma may interact with galactosides. Each of these subdomains has aromatic residues that can interact with the nonpolar face of galactose, and three of the four subdomain folds (1alpha, 1beta, and 2gamma) have polar residues for hydrogen bond formation to the sugar hydroxyls [8950484].

The family 10 xylanase from Streptomyces olivaceoviridis E-86 contains a (beta/alpha)(8)-barrel as a catalytic domain, a family 13 carbohydrate binding module as a xylan binding domain (XBD) and a Gly/Pro-rich linker between them. The crystal structure of this enzyme showed that XBD has three similar subdomains, as indicated by the presence of a triple-repeated sequence, forming a galactose binding lectin fold similar to that found in the ricin toxin B-chain [11829503].

Browse genome assignments for this superfamily. The SUPERFAMILY hidden Markov model library has been used to carry
out SCOP domain assignments to all genomes at the superfamily level.

Alignments of sequences to 34 models
in this superfamily are available by clicking on the 'Alignments' icon above. PDB sequences less than 40% identical
are shown by default, but any other sequence(s) may be aligned. Select PDB sequences, genome sequences, or paste in or upload your own sequences.

Browse and view proteins in genomes which have
different domain combinations including a Ricin B-like lectins domain.

Examine the distribution of domain superfamilies, or families, across the major taxonomic kingdoms or genomes within a kingdom. This gives an immediate impression of how superfamilies, or families, are restricted to certain kingdoms of life.

There are 34 hidden Markov models representing the Ricin B-like lectins superfamily. Information on how the models are built, and plots showing hydrophobicity, match emmission probabilities and insertion/deletion probabilities can be inspected.